Seatbelt assemblies and systems are in widespread use in motor vehicles. Present systems have certain common elements including seatbelt webbing which extends across the upper and lower torso of the occupant, and a retractor for allowing protraction and retraction of the webbing so that the belt may adapt to different sizes of occupants and be conveniently retracted out of the way when not being used. Seatbelt assemblies further typically include a buckle which releasably attaches to a latch plate or tongue.
Seatbelt assemblies must be securely affixed to motor vehicle structural elements in order to provide the necessary restraint effect in vehicle impact conditions and further to meet government regulations. Further, seatbelt assemblies must securely retain an occupant within the seat, while also allowing the occupant easy ingress and egress from the vehicle under a variety of conditions and situations.
Typical seatbelt assemblies include a buckle that is securely mounted to a vehicle structure, such as a seat frame or the floor of the occupant compartment. A tongue (or latch plate) is received by the buckle and is typically attached to the seatbelt webbing. The seatbelt webbing is typically fixed to the vehicle structure at one end, and the opposite end is fixed to a retractor having an internal spool provided to protract and retract the webbing and a lock in impact conditions.
Manufacturers of seatbelt restraint systems and their OEM customers constantly seek to enhance the restraint performance of such systems, both in response to government regulations and consumer demand. With increasing use of seatbelt active type restraint systems, increasing attention is paid to the restraint performance of these systems in impact conditions.
It has been shown in the occupant restraint industry to be beneficial to the occupant in a crash to restrain the occupant's hips as much as possible in order to allow the occupant upper torso to rotate and better utilize the energy management capabilities of the belt system and the frontal impact airbag. One approach to enhance restraint of the hips is to utilize what is known as a crash locking tongue which will lock the belt webbing at the point of transition from the lap to the torso belt sections of the webbing. With a conventional system utilizing a single belt retractor, the tongue (or latch plate) is allowed to slide along the length of the belt webbing enabling it to adapt to different occupant characteristics, seat positions, and other variables. Using a conventional tongue in a frontal impact, the webbing will tend to move from the high load segment (the lap belt portion) to the lower load segment (the torso belt portion). If a crash locking tongue is used in place of a conventional tongue, then the load will not transfer the webbing through the tongue and consequently lower loads are maintained in the torso belt. Although crash locking tongues are used in the industry, but they carry disadvantages in the form of larger size and weight, and higher cost compared to a conventional tongue. This higher weight and cost derive from the fact that there is a specific mechanism inside the tongue that is used to clamp the webbing during a crash.
Some vehicle applications may not need a crash locking tongue to achieve good occupant response. However, these vehicles may still benefit from a tongue which provides higher friction at the lap-torso belt portion transition, and which limits transfer of webbing during a crash without actually locking the webbing.
Also available for motor vehicle applications are tongues which provide increased friction reducing webbing transfer at the lap-torso transition. Such tongues typically utilize specific materials and surface finishes and features for a webbing sliding surface which increases friction, especially when tension is applied to the belt webbing. However, such designs typically have the webbing sliding over the gripping surface during normal use of the belt webbing which may lead to belt abrasion and the degradation of performance of the high friction surface over time.
The present invention is related to a tongue for a belt restraint system that provides higher friction than a standard tongue at the lap-torso transition, but without the locking mechanism of a crash locking tongue and without the above referenced disadvantages. The tongue according to this invention, referred to as a “grip tongue”, will be lighter in weight and more cost effective than a crash locking tongue.